Bike Repair Story (long)
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  1. #1
    B2
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    Bike Repair Story (long)

    Just thought I would share a little bike repair story. No point to it really. Just thought you might get a kick out of how things evolved.

    THE INCIDENT
    I had a little mishap the other day. On the last bit of a descent I downshifted (rings and cogs) just before coming to a stop at a stop light. Pretty normal, right? Well not when you stop pedaling before the “shift” is completed. So… what happens when the light turns green and you’re particularly interested in getting a good bit of acceleration going so you can get out of the way of the traffic? The chain drops off the inside of the small ring, but stays engaged on the bottom of the chainring and you get the chain stuck between the chainring and your chainstay. Ahh… a minor case of chain suck you say? Well not exactly. I’ll get to that… Not realizing what all had happened, I “patched” things back together with about twenty minutes of roadside repair and was still able to get about 20 miles in before I had to go back to work.

    THE PROBLEM (PART I)
    The following afternoon I decided to throw the bike on the stand and get everything adjusted correctly. The first thing I did was pull the crank and inspect the chainstay. I was lucky that the clear chainstay protector tape I put on was very thick. The chain had pretty well destroyed the protector, but left the (carbon) chainstay undamaged. To get the FD to properly clear the chainring, I had to raise it to the highest possible position on the frame braze-on. I couldn’t get the FD stops adjusted without rub on the last three or four cogs in the small chainring. I then noticed that the travel of the chainring had about a 3mm wow in it and the rub was actually coming from chain to chainring, not FD. I didn’t know if it was the spider arm or the chainring that was out whack. I was feeling a little lazy and couldn’t remember the procedure for determining whether the wow is from the chainring or the spider arm so I decided to give the LBS some business.

    THE PROBLEM (PART II)
    The wrench at the LBS took a look at things and recommended getting a new chainring, but offered to tweak the chainring a bit to take the wow out. He did a really nice job of straightening things out and it all looked pretty good. He used a large crescent wrench “clamped” to the chainring and gently tweaked it into shape. I was just about walk out the door when one of the other wrenches there said “let me take a look it”. He looked at it for about 10 seconds and said “your braze-on is bent”. Apparently after the chain dropped off the topside of the ring, but before it sucked into the gap between the ring and the chainstay, the chain “yanked” downward on the rearmost part of the front derailleur and bent the braze-on piece attached to the frame counter-clockwise. The arc of the FD and the chainring were not really even remotely close to parallel. I felt pretty stupid that I hadn’t noticed this myself seeing as the gap between the FD and chainring needed to be more than 5mm at the front of the FD to get about 0.5mm clearance at the rear of the FD. The wrench said that normally he would “tweak” the braze-on back into position, but since this was a carbon frame and the braze-on is riveted to the frame, he didn’t want to touch it. He was saying that the frame “might” be toast and it needed to go back to Colnago in any event. I’ve REALLY enjoyed my C40, but now the “carbon” was loosing a bit of its luster. Sensing my displeasure, the wrench finally says there’s a guy over in our Seattle store that knows Colnagos really well. You should take it over there have him look at it.

    THE FIX
    Now if I had noticed that the braze-on was bent, I would have bent it back myself, but these guys had me freaked out about the whole deal now so I drove into Seattle to see what this other guy might recommend. So what does he say? “It will need to go back to Colnago”. I’m thinking this is going to cost a bundle and I won’t have the bike for probably four months. The only thing worse would be if Colnago looked at and said the frame was toast. Then I’m without the bike for months AND I have to buy a new frame anyway. Finally he looks at a little more and says I can try to straighten it out if you want. I’m thinking that I would rather just order a new frame now versus paying $500 or so and waiting months so I say sure, let’s give it a try. Part of the trick of bending it back was trying not to deform the radius where the FD nestles into braze-on. The wrench did an excellent job. He made sure the braze-on was protected so the wrench didn’t bite into it and then very gently aligned it one little bit at a time, making sure he didn’t go too far. He was quite good. Although the thing that impressed me the most was how in a matter of about 90 seconds he had the front derailleur bolted back on, aligned with the chain ring perfectly, the height adjusted perfectly and both stops adjusted with no rub in any gear combination. Man it probably takes me a half hour to do that.

    I’m sure there are some out there that would say what’s the big deal?; just bend it back and ride on and others that would say this is a serious problem and now your frame has a critical flaw. You’ve got me? I’m just going to go out and ride and not worry about it. My advice is to make sure the downshift you do prior to reaching an intersection is completed before you stop pedaling.

    Bryan

  2. #2
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    Great story, or, umm, nicely told story. Glad it worked out.

    I hope you tipped master wrench $20... $50... or $100.

  3. #3

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    What kind of protector did you use on the chainstay? I gouged my CF chain stay when my chain came off the inner last year. I had it looked at and was told it was not significant damage and I had a LBS do a small repair on it using marine gel coat scratch repair. I would like to put some kind of protector on it just in case it happens again.

    I don't understand why the manufacturers don't protect the cf chain stays more since this seems to be a common problem with chain suck.

  4. #4
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    Quote Originally Posted by BaadDawg
    I don't understand why the manufacturers don't protect the cf chain stays more since this seems to be a common problem with chain suck.
    BaadDawg is my Ottawa doppleganger. We bought the same bike probably less than a week apart I got the same chain suck issue around the same time as him too.
    I Managed to patch up the clearcoat with a bit of clear nail polish. It chewed up the chain stay protector pretty good.
    There has to be a way to prevent this kind of thing. Someone in one of the other threads said that he'd made a chainstay protector out of an aluminum coke can. Struck me as a pretty good idea provided you could make it look alright.

  5. #5
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    I'd highly recommend having at least two bikes--not be able to ride cause one bike is messed up sucks.

    I think they make those front der "braze ons" (not really since it's a carbon frame) pretty soft on carbon bikes. And generally the easiest and safest way to bend 'em is to leave the front der clamped on and tug on the front der to do the actual bending.

  6. #6
    Zeppelin/Ultegra Rider
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    A possible protector:

    Quote Originally Posted by Frith
    There has to be a way to prevent this kind of thing. Someone in one of the other threads said that he'd made a chainstay protector out of an aluminum coke can. Struck me as a pretty good idea provided you could make it look alright.
    Where I work (automotive assembly plant) we apply a clear vinyl-like film to areas of the car that are susceptible to rock chips. I'm not sure where one could purchase this product, but it makes a nice chainstay protector on my bike. It's completely transparent and has a shiny surface, so it looks good on a bike. You might try an auto parts store, or maybe a body shop may be able to help you.
    Ride in Peace....Enjoy every sandwich......Mike

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    B2
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    I thought about leaving the FD on and bending in back using the FD to tug on, but at that stage is was in someone elses hands (so to speak). My other thought was to use an old worn out FD and use that in lieu of using my nice Record FD and making it old rickety before it's time.

    I actually do have another bike I could ride, but I'll tell straight out there is NO comparison between a 16 lb C40 and a 26 lb lugged steel behemoth(sp?). Mind you they each have their own purpose. Not that I couldn't ride the lugged steel frame, but to go through half the summer without the C40... Just because it may be a necessary option doesn't make it a good one.

    As far as the protector tape goes, I'm not sure who makes it. I bought a roll of the stuff from Colorado Cyclist about five or six years ago. It's about 3" wide and maybe ten feet long. I've used it for all kinds of stuff.

    Bryan

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    Well Frith you are one up on me big time with your busted fork and all. WTF has happened with it anyways?

    I think the marine gel scratch remover is alot more heavy duty than nail polish. My lbs did it and he told me what to get. Said he had an Argon 18 Platinum that was really mangled in the chain stay from suck and he managed over a week to build it up with the gel coat to be ok. Had to go to a marina supply place to get it special ordered (they were out of stock on the clear). Not the prettiest though. It's shiny now where it has been applied, as opposed to matt, but it's not exactly a highly visible area.

  9. #9
    Beetpull DeLite
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    Sign shop!

    Quote Originally Posted by 4bykn
    Where I work (automotive assembly plant) we apply a clear vinyl-like film to areas of the car that are susceptible to rock chips. I'm not sure where one could purchase this product, but it makes a nice chainstay protector on my bike. It's completely transparent and has a shiny surface, so it looks good on a bike. You might try an auto parts store, or maybe a body shop may be able to help you.
    Any sign shop in your town should carry a huge assortment of vinyl on large rolls....so not only could you get clear, but black, chrome, silver metallic, and a ton of other solid and specialty colours. The premium ones (clear falls into that category) are thinner, so you might need two or three coatings.

    Can't remember how much they cost though...which is sad, since I've worked at two sign shops.

    Or you could do what Mongoose did for their old mountain bikes, like mine shown here....a strip of metal cut out and adhered to the frame.
    Attached Images Attached Images

  10. #10
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    Quote Originally Posted by BaadDawg
    Well Frith you are one up on me big time with your busted fork and all. WTF has happened with it anyways?
    .
    Keep meaning to give an update on that... look out for it in coming days.

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